move a pin on google map

The event handlers in this page are using event handlers from the Google Maps API.
You can find this detail here:
https://developers.google.com/maps/documentation/javascript/events#EventProperties
and more specifically here:
https://developers.google.com/maps/documentation/javascript/examples/event-click-latlng

There are conversations on stackoverflow if you get stuck:
https://stackoverflow.com/questions/6374329/get-latitude-and-longitude-of-marker-onclick/9057674
https://gis.stackexchange.com/questions/33238/getting-coordinates-from-click-or-drag-event-in-google-maps-api
https://stackoverflow.com/questions/17889748/displaying-latitude-and-longitude-on-marker-click-event

If you’re not comfortable building this out on your own with the API, then there may be some options to you from ACF:
https://www.advancedcustomfields.com/resources/google-map/
or this one:
https://en-ca.www.ads-software.com/plugins/wp-google-map-plugin/